1. Field of Invention
This application relates to a tracking device, having one controllable degree of freedom, that is movable with three degrees of freedom.
2. Description of Related Art
Tracking devices may be used in areas such as planetary exploration, mobile remote sensing, tracking of moving land-based agents such as people, animals, and automobiles, tracking of flying objects, automatically deployable perimeter sensors, toys, sound input/output device which follow a user for example for actors on a stage, for mobile phone users, a computer input device that follows a mobile user, and smart bombs. However, in order for the tracking device to translate in a three dimensional space, complicated propulsion and control systems are necessary. This results in tracking devices of increased cost and size.
Eukaryotic single-celled micro-organisms function as tracking devices in a neutrally buoyant medium, but are capable of controlling only one degree of freedom. The micro-organisms are capable of movement in a three dimensional space, however, move toward and away from a sensed stimuli, such as food sources and light. The micro-organisms control their one degree of freedom to essentially move forward in a helical pattern. The micro-organisms track a stimuli by modulating the speed of their one degree of freedom motion through a simple feedback system. As the microorganism spins around, it senses the stimuli sinusoidally. By modulating its spinning speed in a manner directly proportional to the sensed stimuli, the micro-organism moves toward, or away from, depending on the sense of modulation, the stimuli by precession, i.e., the motion of an axis of the microorganism due to an applied external force. The motion of single-celled micro-organisms is described more thoroughly in xe2x80x9cOrientation by Helical Motion-I. Kinematics of the Helical Motion of Organisms with up to Six Degrees of Freedom,xe2x80x9d by Hugh C. Crenshaw, published in the Bulletin of Mathematical Biology, Vol. 55, No. 1, pp. 197-212 (1993), incorporated herein by reference in its entirety.
Propeller-driven aerial toys and amusement devices are known, for example, from U.S. Pat. No. 4,271,629 and 3,603,033. U.S. Pat. No. 5,533,920 to Goodwin discloses a propeller-driven aerial toy having front and, rear propellers driven by a rubber-band motor and a lock and release mechanism usable to control the rotation of the propellers. U.S. Pat. No. 3,603,033 to Mueller discloses a flying rotorcraft toy having a driven propeller mounted in a duct. Lifting rotor blades extend from the top of the duct. The duct and blades rotate oppositely to the propeller, due to torque. The lift of the blades thus adds to the lift provided by the propeller for vertical propulsion.
The flying toys discussed above include complicated transmissions and are not capable of tracking a target. The flying toys also require initiation and supervision by an operator and are operable only with a limited type of power supply.
This invention provides a tracking device that is movable with three translational degrees of freedom under gravity by controlling movement with one degree of freedom without explicit orientation toward a target.
In various exemplary embodiments of the tracking device according to this invention, the tracking device includes a motor, top and bottom propellers of opposite sense attached to the stator and rotor of the motor for rotation in opposite directions. Target sensors are provided on the propellers and signals from the target sensors are supplied to a controller that controls the rotation of the motor and the propellers. The tracking device also includes a power supply for the motor and the controller.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.